1. Field of the Invention
The present invention relates to a closure for the discharge opening of a steel reheat furnace comprising sag-resistant metal alloy mesh curtains formed from plural steel mesh ribbons. The metal alloy mesh curtains also may be employed in the charging opening of certain reheat furnaces. The purpose of the metal alloy mesh curtains is to retain heat energy within the reheat furnace by reducing the opportunities for heat to leave the furnace.
2. Description of the Prior Art
Steel reheat furnaces are employed to reheat steel workpieces to a temperature at which the steel may be mechanically worked outside the reheat furnace. U.S. Pat. Nos. 3,148,868; 3,716,222; 3,749,550; 4,427,371. The steel workpieces are heated to temperatures of 2000.degree. F. and higher. The reheat furnaces have refractory ceilings, side walls and floors and include plural heat sources such as gas burners or radiant gas burners. Horizontal rails are mounted within the furnace to support steel workpieces as they move through the furnace from a charging opening at one end to a discharge opening at the other end. The temperature gradient across most reheat furnaces develops the highest temperatures adjacent to the discharge opening and usually significantly lower temperatures adjacent to the charging opening. A refractory slab customarily is positioned within the furnace adjacent to the discharge opening. Multiple slots are presented within the refractory slab to receive fingers for directing and withdrawing the forward-most workpiece from the refractory slab through the discharge opening.
With the advent of high temperature radiant heaters, it is now possible to develop high temperatures within a reheat furnace adjacent to the charging openings. Reheat furnaces provided with high temperatures adjacent to the charging openings will benefit from the curtains of this invention. Such installation will be separately discussed in this specification which is principally concerned with discharge openings.
Heated steel workpieces are removed from the reheat furnace through the discharge opening, and new workpieces are introduced through the charging opening whereby a continuous inventory of steel workpieces at gradually increasing temperatures is maintained inside the reheat furnace. Customarily the discharge opening is in line with the movement of steel workpieces through the furnace; however the discharge opening may be angled with respect to the line of movement, e.g., U.S. Pat. No. 4,492,565.
Customarily one or more vertical steel or composite assemblies are provided to function as doors at the charging opening and at the discharge opening. U.S. Pat. No. 4,669,939. The doors are raised vertically by cables to expose the charging opening or discharge opening and the doors are maintained in an elevated position until a steel workpiece or workpieces enters the charging opening or is withdrawn through the discharge opening. Immediately thereafter the doors are lowered to obstruct heat loss through the openings. A significant heat loss occurs during the time when the doors are elevated and the openings are exposed. The heat loss is usually greatest at the discharge opening where the temperatures the highest in the structure.
It is known to employ steel mesh curtains at the charging opening of a reheat furnace which heretofore experienced elevated temperatures of the order of 1500.degree. F. At these temperatures, woven mesh curtains of ordinary steel are not adversely affected by the temperature exposure. However steel mesh curtains have not been employed at the discharge opening of reheat furnaces where the furnace heat loss can be severe.
Some reheat furnaces may experience much higher temperatures as a result of recently available radiant heat sources which can be located adjacent to the charging opening of reheat furnaces. In such reheat furnaces, the curtains of this invention will provide reliable heat retention.